Lag fuse



Oct. 7, 1952 G. F. LAING LAG FUSE Filed Oct. 25, 1950 mm Q QN mm mm m 4mfl M E Q Q m wy QM WMMM @NQN MN Patented Oct. 7, 1952 LAG FUSE,

Gordon F. Laing, Delavan, Wis., 'assignor to Economy Fuse andManufacturing 00., Chicago, 111., a corporation of Illinois ApplicationOctober 23, 1950, Serial No. 191,627

The present invention relates to improvements in lag fuses.

More particularly, the present invention relates to the type of electricfuse which will open an electric circuit promptly upon a high surge ofcurrent, such, for example, as accompanies a short circuit,.:but willdelay the opening of the electric circuit for predetermined periods uponmoderate overloads such as those frequently encountered in motor.starting operations.

Though a preferred embodiment of the present invention has beenillustrated in a non-renewable fuse of the ferruletype, it will beunderstood as the description proceed-s that th ..invention is equallyapplicable to other types of fuse.

An object of the present invention is to provide a lag fuse which isdependable in protecting an electric circuit under conditionsapproximating short circuit, but will delay for predeterminablelongperiods the opening of the circuit upon moderate overloads.

A further object is to provide a lagfuse of the type just referred towhich is relatively simple to manufacture and dependable in service,

A further object is to provide a lag fuse of a relatively high heatcapacity whereby moderate overloads may be carried for prolonged periodsof time with assurance that the circuit will be openedwhen apredetermined product of overload and time factors has been reached.

A further object is to provide a lag fuse Well adapted tomeet the needsof ordinary service.

Other'objects will appear as the description proceeds.

Referring to the drawings- Figure l is a longitudinal sectional viewillustrating a preferred embodiment of the present invention, the partsbeing shown in current passing relationship with one another; and

Figure 2 is a view similar to Figure l, but showing the parts located inpositions they will assume when the fuse has operated to break thecircuit after the lapse of a predetermined period of overload.

The numeral l indicates a tube which according to usual practice may becomposed of fiber or the like. Located at the two ends of the tube Itare the ferrules II and l2, which are cup-shaped members closelyreceiving the ends of the tube It. Said ferrules l l and I2 are slottedin their bottom portions to receive extremities of fuse links to bereferred to presently. Said extremities of said fuse links are solderedor otherwise electrlcally connected to said ferrules I l and l2.

5 Claims. (Cl. zoo-12s) Located within the tube It is a fuse assemblyindicated as a whole by the numeral I3; Said fuse assembly I3 iscomposed essentially of the slugheat reservoir 14, the tubular heatreservoir l5, the plunger reservoir [6, portions of low melt ing pointeutectic solder Zita and 2% connecting said reservoirs l4 and i5 andsaid reservoirs l6 and i5, respectively, the spring l1 and the fuselinks H 8 and it, which fuselinks comprise heating members for saidreservoirs and said portions of solder. The fuse links it and 19 areelectrically and mechanically united to the slug heat reserwithrestricted portions It and 2|, respectively,

or a plurality of such restricted portions, according to usual practice.

=Located upon and fitting the fuse links [8 and 19, respectively, arefiber washers 22 and 23, which fiber w'asherstogether with the twoferrules H. and I2 provide chambers 24 and 25, respectively, at the twoends of the fuse for receiving quenching powder. Between the two washers22 and 23 is the chamber 25 receiving the slug heat reservoir 14, theplunger'reservoir IS, the tubular reservoir l5, together with the springl1, and the two portions 26a and 26b of low melting point eutecticsolder for holding said reservoirs in series relationship against thetension of said spring.

The plunger reservoir I6 has the head portion 21 and the shank portion28, which shank portion fits loosely within a corresponding hole in thetubular reservoir l5. The fit between the shank portion 28 and thetubular reservoir l5 should not be so close that compressed air willretard the movement of said shank 28 into said tubular reservoir IS.

The plunger reservoir 5 is urged toward the right as the parts areviewed in the drawing by the spring l1, the left hand convolutions ofwhich are threaded onto a corresponding groove in the head portion 21 ofsaid plunger reservoir I8. The

outer diameter of the tubular reservoir I5 is of a size to receive thecoil spring I1. Said tubular reservoir [5 at its right hand end isprovided with an end portion 29 of reduced diameter, providing ashoulder for receiving the right hand end convolution 30 of the springI1. In other words, the

' [6 into the tubular reservoir 15 and away from the slug heat reservoirM.

The mode of operation of the above described embodiment of the inventionwill1be clear with-- out detailed-explanation. When the-fuse is lo--cated in an electric circuit, said fuse will protect such circuitagainst conditions approximating short circuit for the reason that thefuse links lit and I9 will fuse in the manner well understood under suchshort circuit conditions;

Under overload conditions the. fuse.- links; is and [9 will warm up,acting as heaters com municating heat to the members. l4, |5,-an cl--[6,. which, being heat reservoirs, will store up such heat to apredetermined extent, depending. jointly upon the degree of. overloadand the prolongation: of; the. period: Qfioverload. The; melting: pointof; the: utectic older; uniting; the,

the tubular reservoir" 1 5; may be accurately; pre.

determined; and:v when sufficient-heat has. been.

storediinzthe members; It; lfifandlfirtomelt, this.

eutectic-rsolder,. the. spring; I]: will; move, the:

plunger; reservoir I51 to. the. right; effectually; opening. the:circuit between .the. slug heatreservoir: I14; andjthe, plunger;-reservoir l5;- thereby.

titions. in said casing; dividing; it-;into:. end: and

central: compartments, fuse. links. in: said: end. compartments eachextending between the ad.- jacent casing terminal and th proximatepartitioninto the central compartment; the terminus of. each. link in.the central compartment. being: inispaced relation. to'; the: opposite.lil'lk'l terminustherein; a. relatively massive-.metallic conductor oflarge thermal .capacityr bridging. and. connect--- ing; the. linkterminals .in the: central cnmpantsment, said; massive conductor: being:formed" in: three. parts: one partof which; is connected in.

permanent mechanical i and electrical union. with: theterminus ofronefuse link;- an; opposite: part:

which. is; simiiarlynonnectedto the opposite-fuse 4 link terminus inspaced relation to said one part, and a connecting part in telescopingengagement with said one part and joined to it and to said opposite partby low meltingpoint solder: and a spring extending under tension betweenthe telescoped parts when the three parts are soldered together so as tobias the connecting part awamfromsaid oppositepert 2i Thfuse-construction specified in claim 1, in which said spring is ahelical spring within the bore of which said telescoping parts areaccommodated, one convolution of said spring being sufficiently reducedin diameter to engage an axial; bearing; on; one. of said telescopingparts.

* the other ofsaidtelescoping parts having screwthreads complementary tothe convolutions of said. spring whichare screwed into engagement withthe latter when telescoped relative to the other part.

3. The fuse construction specified in claim 1, the-end; chambers oiisaidcasinsabeingfllledrwith quenching powder in which said fuse are;

embedded;

of each; other into. and out of; abutting; relation to. thethird part;and a helical: spring tending to withdraw said sliding. parts fromabutment: withsaidathirdapart;andlow-melting=point:solder" holdingsaidithree partsxinr abutting relation;

5; The lag. fuse assembly specified in claim- 4, in. which: said-shelical spring. has convolutions at one. of itsends in. screw-threadedengagement with. one of sai'dglsii'ding parts, and a constrictedconvolution at; its. opposite end: bearing upon a portion of reduceddiameter on theother slid ing part; said; parts being: coaxial with saidspring,

and withreach other.

GORDON F.

REFERENCES L GIZDEDi The foliowing references are of record in the fileof this patent-i.

UNITED STA ES'P T N Number N amev Date- 2,044 22c: Rawlin'si i Juno-16;rm: 23211311 I aylor June 1531 943

